beginning of a dns lexer

dns.y

@@ -58,3 +58,100 @@ func (DnsLex) Lex(yylval *yySymType) int {
 
     return 0
 }
+
+
+func isSeparator(c byte) bool {
+	switch c {
+	case '(', ')', '<', '>', '@', ',', ';', ':', '\\', '"', '/', '[', ']', '?', '=', '{', '}', ' ', '\t':
+		return true
+	}
+	return false
+}
+
+func isSpace(c byte) bool {
+	switch c {
+	case ' ', '\t', '\r', '\n':
+		return true
+	}
+	return false
+}
+
+func isCtl(c byte) bool { return (0 <= c && c <= 31) || c == 127 }
+
+func isChar(c byte) bool { return 0 <= c && c <= 127 }
+
+func isAnyText(c byte) bool { return !isCtl(c) }
+
+func isQdText(c byte) bool { return isAnyText(c) && c != '"' }
+
+func isToken(c byte) bool { return isChar(c) && !isCtl(c) && !isSeparator(c) }
+
+// This is a best effort parse, so errors are not returned, instead not all of
+// the input string might be parsed. result is always non-nil.
+// must never begin with a string
+func scan(s string) (string, int) {
+        if len(s) == 0 { 
+                println("a bit short")
+        }
+	raw := []byte(s)
+	chunk := ""
+        off := 0
+        brace := 0
+redo:
+	for off < len(raw) {
+		c := raw[off]
+//                println(c, string(c))
+		switch c {
+                case '\n':
+                        // normal case??
+                        if brace > 0 {
+                                off++
+                                continue
+                        }
+		case '.':
+//                        println("off", off)
+                        if off == 0 {
+                                print("DOT")
+				return ".", off + 1
+                        } else {
+                                return chunk, off
+                        }
+                case ' ','\t':
+                        if brace != 0 {
+                                off++
+                                continue
+                        }
+                        // eat whitespace
+                        // Look at next char
+                        if raw[off+1] == ' ' {
+                                off++
+                                continue
+                        } else {
+                                // if chunk is empty, we have skipped whitespace, and seen nothing
+                                if len(chunk) == 0 {
+                                        off++
+                                        goto redo
+                                }
+                                print("VAL ")
+                                return chunk, off
+                        }
+                case '(':
+                        brace++
+                        off++
+                        continue
+                case ')':
+                        brace--
+                        if brace < 0 {
+                                println("syntax error")
+                        }
+                        off++
+                        continue
+		}
+                if c == ' ' { println("adding space") }
+                if c == '\t' { println("adding tab") }
+                chunk += string(c)
+		off++
+	}
+        print("VAL ")
+	return chunk, off
+}